Numerous feeding experiments in this country and abroad have demonstrated
the efficacy of feeding high levels of copper to pigs to improve feediot per-
formance (1). However, very little experimentation has been undertaken to
determine practical approach to the use of copper in the free-choice system
of feeding. -Inra previous study from this station (2) it was reported that
1000 ppm of.copper added to the protein supplement was excessive. Intake of
supplement was depressed below that necessary for good performance. The
present experiment was undertaken to obtain information on the use of lower
levels of copper in the supplemental mixture.

Procedure

Sixty-four crossbred pigs (Landrace-Duroc x Hampshire) were divided into
8 lots of eight pigs each. Average initial weight was approximately 83 lb.
Four lots were composed of gilts and four lots were composed of barrows. One
lot from each sex group was fed on each of the following treatments.

Treatment 1 Shelled yellow corn and supplement free-choice (control).

Treatment 2 Shelled yellow corn and supplement free-choice. Two
hundred and fifty ppm copper as CuS04 was added to
supplement.

Treatment 3 Shelled yellow corn and supplement free-choice. Three
hundred and fifty ppm copper as CuSO4 was added to
supplement.

Treatment 4 Shelled yellow corn and supplement free-choice. Four
hundred and fifty ppm copper as CuS04 was added to
supplement.

Composition of the protein supplement is presented in Table 1.

All pigs were slaughtered at the termination of the experiment and carcass
data were obtained according to standard procedures. Liver samples were taken
from all pigs and analyzed for residual copper.

J/ Supported in part by grant-in-aid from International Copper Research
Association, Inc., New York, New York.

A summary of performance is presented in Tables 2 and 3. During the first
28 days (Table 2) all male groups receiving copper in protein supplement appeared
to respond in rate of gain. This was not true in case of the females. The intake
of protein supplement relative to corn consumption was variable from pen to pen
but was generally quite acceptable in terms of known protein requirements. The
females consumed less protein supplement than the barrows. It might have been
anticipated that the reverse would have been true in view of the fact that
previous tests have shown that gilts require a higher level of protein in the
diet for optimum performance and carcass leanness. It was calculated that the
gilts consumed feed containing an average of 15.7% protein while for the barrows
it was 16.0%. The estimated copper intake increased as the level of the copper
in the supplement was increased. The highest level of copper in the supplement
(450 ppm) induced an intake of approximately 100 ppm. Based on other investi-
gations this level of copper may be adequate to improve feedlot performance.
However, levels ranging from 125-250 ppm are probably somewhat more effective.
The level of copper added to the supplement did not seem to be related in any
clear pattern to supplement intake. Levels up to 450 ppm appeared to be toler-
ated with no significant influence on feed intake patterns.

For the entire experiment (Table 3) there was no clear indication that the
copper supplemented pigs had responded in rate of gain. One group of males
(Lot 3-A) gained somewhat faster than all other lots with this advantage coming
about after the first 28 days. This could have been due to a combination of
copper intake and ideal supplement to corn ratio intake for this lot. For the
overall experiment the males consumed slightly more protein than the females
(14.9 vs. 14.6%). As would be expected the consumption of supplement decreased
relative to the consumption of corn as the pigs became heavier. As the protein
supplement intake gradually decreased so did the copper intake. Maximum supple-
mentary copper intake for the overall trial averaged approximately 80 ppm for

Table 2. Influence of various copper levels in supplement on feed intake and gains of pigs.
(First 28 days)

I/ One pig was removed from this lot early in the expt. Data are based on the seven remaining
animals.

2/ Based on added copper only.

the pigs supplemented at the highest level (450 ppm). The feed intake data
suggested no clear effect of supplement copper level. Pigs did not reject
supplement when copper was included at levels of 250, 350 and 450 ppm, nor was
there evidence that acceptability was enhanced by any of the levels of supple-
mentation.

Carcass data and copper liver analyses data are summarized in Table 4.
The various levels of copper supplementation did not appear to influence the
carcass measurements. As would be expected the females yielded leaner car-
casses than the males as measured by backfat thickness, loin eye marbling,
loin eye area and percent 4 lean cuts. Liver copper accumulations were not
great at any level of copper supplementation. Only slight increases were
apparent and these were greater for the females than for the males.

Summary

Sixty-four pigs were used in a feeding-slaughter experiment to evaluate
certain levels of copper when added to the protein supplemental mixture of
pigs fed in the free-choice system. Levels of 250, 350 and 450 ppm copper
as CuSO4 were studied.

Pigs consumed supplement and shelled corn in reasonable ratios at all
levels of copper supplementation. There was no indication that the copper
affected feed intake. Barrows tended to consume somewhat more protein than
the gilts. During the first four weeks the calculated level of protein for
the total feed mixture consumed was 16.0% for the barrows and 15.7% for the
gilts. For the entire experiment these values were 14.9% and 14.6%.

Except for one pen of barrows (350 ppm Cu) there was no indications of
a performance response to copper supplementation. The overall copper intake
for pigs supplemented at the highest level was calculated as 80 ppm. This is
somewhat less than the 125-250 ppm considered necessary for growth responses.

the pigs supplemented at the highest level (450 ppm). The feed intake data
suggested no clear effect of supplement copper level. Pigs did not reject
supplement when copper was included at levels of 250, 350 and 450 ppm, nor was
there evidence that acceptability was enhanced by any of the levels of supple-
mentation.

Carcass data and copper liver analyses data are summarized in Table 4.
The various levels of copper supplementation did not appear to influence the
carcass measurements. As would be expected the females yielded leaner car-
casses than the males as measured by backfat thickness, loin eye marbling,
loin eye area and percent 4 lean cuts. Liver copper accumulations were not
great at any level of copper supplementation. Only slight increases were
apparent and these were greater for the females than for the males.

Summary

Sixty-four pigs were used in a feeding-slaughter experiment to evaluate
certain levels of copper when added to the protein supplemental mixture of
pigs fed in the free-choice system. Levels of 250, 350 and 450 ppm copper
as CuSO4 were studied.

Pigs consumed supplement and shelled corn in reasonable ratios at all
levels of copper supplementation. There was no indication that the copper
affected feed intake. Barrows tended to consume somewhat more protein than
the gilts. During the first four weeks the calculated level of protein for
the total feed mixture consumed was 16.0% for the barrows and 15.7% for the
gilts. For the entire experiment these values were 14.9% and 14.6%.

Except for one pen of barrows (350 ppm Cu) there was no indications of
a performance response to copper supplementation. The overall copper intake
for pigs supplemented at the highest level was calculated as 80 ppm. This is
somewhat less than the 125-250 ppm considered necessary for growth responses.